1. Field of the Invention
This invention relates generally to lumber handling and sorting equipment, and more particularly to lumber edging picker conveyors.
2. Description of the Prior Art
In a lumber mill, rough boards which are cut from a log are sent through an "edger," where bark and board edges of uneven outline are removed to leave a board of substantially rectangular cross section. The edger typically has two or more spaced apart, side-by-side circular saws, through which a wide, untrimmed board or lumber slab is conveyed lengthwise. In addition to trimming off rough outside edges, the edger often performs longitudinal cuts on the boards, thereby dividing each board into two or more narrower boards.
During this trimming or "edging" operation, the narrow, rough strips or "edgings" are removed from the lumber and must somehow be isolated from the boards downstream of the edger saws. Optimum efficiency usually results if, on leaving the edger, the edgings are immediately separated out from the flow of boards, enabling the boards to be further processed without encumbrance by the edgings. Once the edgings are separated out, they are chipped, burned, or otherwise treated. The equipment for performing this separating function is typically referred to as an edging picker outfeed conveyor.
Conventional outfeed conveyors are disclosed in U.S. Pat. Nos. 3,139,125 and 3,017,909 and are marketed by Schurman Machine Works, Inc., and Portland Iron Works. The principle of operation of the conveyors disclosed in these patents and of the Schurman and Portland conveyors is basically the same. The outfeed conveyor has a first fixed "fence" which is aligned with a first fixed edger saw, which cuts off one rough edging. The outfeed conveyor also has a movable fence, which is aligned with and moves with a second laterally movable saw or a third saw if the lumber slab is to be cut into two narrower boards. In any event, the movable fence is typically aligned with the saw that cuts off the second rough edge. As the lumber moves through the edger saws, the waste edging from the first saw is diverted by the first fixed fence to one side of the outfeed conveyor. The edging cut by the second or third saw is diverted by the movable fence to the other side of the outfeed conveyor. The finished lumber, cut to width, moves over the outfeed conveyor between the fences.
Variations of these basic prior art edging picker outfeed conveyors are disclosed in the following U.S. patents: U.S. Pat. No. 1,724,042 uses a fixed shear strip with a wedge-shaped downstream end portion to divert edgings laterally from the edged lumber (see FIG. 8); U.S. Pat. No. 2,468,036 uses rollers with one set of enlarged ends aligned with the saw blade to cause a slab cut from a log to lie flat as it is diverted sideways after being separated from the log; U.S. Pat. No. 3,687,269 uses a conventional edging picker along with sweep plates or fingers; and U.S. Pat. No. 3,732,765 uses sweep fingers to separate and divert cut lumber in desired directions on an outfeed conveyor.
A second type of conventional edging picker outfeed conveyor is disclosed in the U.S. Pat. No. 3,225,800. The apparatus disclosed in this patent uses a pair of outfeed conveyor belts downstream of the edger, with both belts being laterally displaceable so that one belt is always aligned between the fixed and one movable saw, while the other belt is always aligned between the one movable saw and a second movable saw. The belts are driven and appear to be the principal outfeed conveyor means for the edged lumber. Although it is unclear from the patient, it appears that the edgings drop to opposite sides of the two belts.
All of the above-described systems are relatively complex in design and therefore involve a substantial capital investment to purchase. Because of this complexity, they can also be difficult and therefore expensive to maintain. In normal operation, wearing of the components can result in inaccuracy which can dramatically affect the performance of the system because precise adjustment of the various components is often essential to ensure proper operation. Another problem with many prior art designs, which is particularly noticeable with respect to the system disclosed in U.S. Pat. No. 3,225,800, is that the operator must wait until lumber is downstream of the edging picker conveyor before resetting the position of the edger saws. If this is not done, there is a good chance of losing lumber off of the belts as they shift in a lateral direction. Since the saws must often be reset after each board has passed through, the necessity of having to wait for the prior board to clear the conveyor dramatically reduces the output of the edger.
Hence, it is a primary object of the present invention to provide an improved lumber sorter which effectively and reliably overcomes the aforementioned limitations and drawbacks of the prior art proposals. More specifically, the present invention has as its objects one or more of the following, taken individually or in combination:
(1) The provision of an edging picker conveyor which can operate at higher speeds by permitting transverse adjustment of the edger saws while the board which has just passed through the saws is still on the edging picker conveyor;
(2) To develop an edging picker conveyor in which the settings and adjustments need not be as precise as with the prior art proposals, thereby simplifying operation and eliminating the requirement of costly and complicated control mechanisms;
(3) To provide a lumber sorter which is simple in construction and therefore is relatively inexpensive to purchase and is reliable, requiring a minimum of maintenance; and
(4) The development of an edging picker conveyor which is narrower than prior art designs and is adapted to eject edgings downwardly rather than laterally, thereby facilitating the use of a greater number of picker conveyors in any given space.